Knock Sensor: Testing and Inspection

Knock Sensor, Checking

The following procedure is used to diagnose Knock Sensor (KS) 1 (G61)/Knock Sensor (KS) 2 (G66).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The mounting bolt of Knock Sensor (KS) 1 (G61)/Knock Sensor (KS) 2 (G66) tightened to 20 Nm.

• The Motronic Engine Control Module (ECM) (J623) fuses OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, shift selector lever into position " P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

- Remove the engine cover with air filter.

- Disconnect Knock Sensor (KS) 1 (G61) electrical harness connector- 2 - or Knock Sensor (KS) 2 (G66) electrical harness connector - 3 -.





Checking internal resistance

- Using a Multimeter, check the Knock Sensor terminals 1 to 2 for an internal short.









Specified value: infinite (Infinity).

If any of the specified values are not obtained:

- Replace the faulty Knock Sensor.

If the specified value was obtained:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module J623, Replacing ] Motronic Engine Control Module J623, Replacing.

- Using a Multimeter, Check the Knock Sensor electrical harness connector to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 for an open circuit.













Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).

- Check the wiring connection for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring and the resistance was not OK:

- Replace the faulty Knock Sensor.

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module J623, Replacing ] Motronic Engine Control Module J623, Replacing.

- Assembly is performed in the reverse of the removal.

Final Procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

End of diagnosis.